Analysis of retro-reflective surfaces for urban heat island mitigation: A new analytical model

Solar reflectance of buildings’ envelope and urban paving represents an important optic-energetic property for the characterization of building energy performance for cooling and to reduce the urban heat island effect. Together with the emissivity, it represents the main feature contributing to the overheating reduction of a surface exposed to sunlight. Additionally, solar reflectance depends, among other factors, also on the angular distribution of the incident energy Additionally, solar reflectance depends on the angular distribution of the incident energy, which effect is rarely taken into account to estimate its cooling potential. This paper deals with an experimental and analytical study for the assessment of the angular reflectance of retro-reflective films. An ad hoc experimental facility is designed to measure the angular reflectance of retro-reflective samples. Measurement results are used to determine an original analytical model which describes the optic-energy behavior of retro-reflective materials. The experimental campaign and a novel analytical model showed that retro-reflective materials could be effectively applied as coatings on urban paving and building envelope, in order to reflect the solar radiation beyond the urban canyon and the urban canopy in general.